RADAR SPEED CAMERAS and HOT DAYS

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Discussion Overview

The discussion revolves around the potential effects of high surface temperatures on RADAR speed cameras, particularly in the context of their accuracy and reliability in measuring vehicle speed. Participants explore various factors that could influence the readings of these devices, including the impact of air temperature, calibration issues, and the specific technology used in different types of RADAR systems.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that high surface temperatures could affect the frequency of RADAR signals, potentially leading to false high readings.
  • Others argue that the effect of temperature on the speed of light is negligible and unlikely to have a practical impact on RADAR speed measurements.
  • Concerns are raised about the accuracy of GPS systems in measuring speed, with some participants noting that GPS can have significant errors.
  • One participant questions whether only certain types of RADAR speed cameras are affected and discusses the possibility of faulty equipment being introduced.
  • There is mention of legal rights regarding the calibration and operation of RADAR speed cameras, with suggestions to consult a lawyer for advice.
  • Some participants describe the specific technology of the Gatsometer Digital Radar System-Parabolic, including its method of measuring speed through Doppler shift and the implications of road surface temperature on signal accuracy.
  • Questions are posed regarding the purpose of bouncing the RADAR beam off the ground at an angle rather than directly off vehicles, with some suggesting it may primarily serve as a trigger for the camera.
  • Concerns are expressed about the calibration of RADAR devices, particularly if they are designed for different environmental conditions.
  • Participants discuss the mechanics of how speed is measured using photographs taken at fixed intervals, contrasting this with handheld devices that rely on Doppler effect measurements.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether high temperatures significantly affect RADAR speed camera readings. Multiple competing views exist regarding the influence of temperature, calibration issues, and the technology used in different RADAR systems.

Contextual Notes

Limitations include the potential for missing assumptions about the operational environment of the RADAR systems and the specific calibration standards that may vary by region.

PNutt
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Hi all

Is it possible that a RADAR speed camera, (the type that bounces off the road and is reflected off the vehicle and then the doppler shift represents the vehicle speed) can be affected by a raise in surface temperatue on a very hot day(40 degrees C plus, poster is in Australia)

I believe that the temp of the road my affect the frequency of the RADAR signal giving false high readings.

We have hundreds of people being fined and losiing their licences here, and it would appear that all GPS, cruise control and speedo in the state of Victoria are faulty, not the camera.

Any help greatly appreciated
 
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No, not to the extent that it would any practical effect (the speed of light does depend on the temperature of the air, but it is an extremely tiny effect).

And, yes, GPS is not necessarily very accurate when it comes to measuring speed.
 
PNutt said:
Hi all

Is it possible that a RADAR speed camera, (the type that bounces off the road and is reflected off the vehicle and then the doppler shift represents the vehicle speed) can be affected by a raise in surface temperatue on a very hot day(40 degrees C plus, poster is in Australia)

I believe that the temp of the road my affect the frequency of the RADAR signal giving false high readings.

We have hundreds of people being fined and losiing their licences here, and it would appear that all GPS, cruise control and speedo in the state of Victoria are faulty, not the camera.

Any help greatly appreciated

Is only one certain (new?) type of RADAR speed camera affected? Sometimes there has been faulty equipment introduced.

What are your legal rights as a driver? Can you demand proof that the device was working correctly and has been calibrated according to rules? Ask a lawyer.

Once the simple causes are excluded, one might look what effect the air temperature gradient has on the radar waves.
 
f95toli said:
No, not to the extent that it would any practical effect (the speed of light does depend on the temperature of the air, but it is an extremely tiny effect).

And, yes, GPS is not necessarily very accurate when it comes to measuring speed.



Thanks

My understanding is that a GPS is accurate to +/- 0.1% at 100 kph, when cruising at a steady speed, update lag not a problem then
 
A.T. said:
Is only one certain (new?) type of RADAR speed camera affected? Sometimes there has been faulty equipment introduced.

What are your legal rights as a driver? Can you demand proof that the device was working correctly and has been calibrated according to rules? Ask a lawyer.

Once the simple causes are excluded, one might look what effect the air temperature gradient has on the radar waves.

Thanks for the reply

The type of camera in question is a Gatsometer Digital Radar System-Parabolic, it focuses a narrow beam on the centre of the lane at a 30 degree, angle the reflected beam from the vehicle is then processed looking at the doppler shift and the speed interpolated from this. As I understand it is supposed to be accuarate to +/- 3 kph so this is subtracted from the "Actual" measured speed. I was wondering if the road surface, being hot, could in some way affect the carrier frequency, I don't know how much the signal would change as a function of a vehicles speed, but i suspect, given the high carrier frequency, this would be quite small, thus a small error would give a false reading?
 
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The radar is affected by the temperature of the air but as f95 said, it's parts per million.
It's possible the unit itself could be out of calibration if it was designed for the Netherlands and is being operated at 50C in Oz - even if it wasn't you might be able to get off if the temperature was officially outside the unit spec.

Generally fixed Gatso's don't clock you based on the radar - they take two photographs a fixed time apart and measure the distance you have gone. The radar is just to trigger the camera for likely 'victims'
 
PNutt said:
Thanks for the reply

The type of camera in question is a Gatsometer Digital Radar System-Parabolic, it focuses a narrow beam on the centre of the lane at a 30 degree, angle the reflected beam from the vehicle is then processed looking at the doppler shift and the speed interpolated from this. As I understand it is supposed to be accuarate to +/- 3 kph so this is subtracted from the "Actual" measured speed. I was wondering if the road surface, being hot, could in some way affect the carrier frequency, I don't know how much the signal would change as a function of a vehicles speed, but i suspect, given the high carrier frequency, this would be quite small, thus a small error would give a false reading?

What is the purpose of bouncing the beam off the ground at the 30 degree angle? Why not just bounce it off the car directly like most other radar speed guns?
 
berkeman said:
What is the purpose of bouncing the beam off the ground at the 30 degree angle? Why not just bounce it off the car directly like most other radar speed guns?


That's what the standard blurb says, as the poster above states it's just a trigger
 
PNutt said:
That's what the standard blurb says, as the poster above states it's just a trigger

Ah, thanks. I'd missed that -- we were posting at the same time.
 
  • #10
I know that here in the UK you can demand a copy of the most recent calibration certificate for the camera. There are certain rules governing this which your lawyer would be well aware of.
If the camera is the usual Gatso type, as stated upthread the speed is measured from 2 photos taken at a fixed interval. The distance you traveled in that time is measured from the road markings.
There have been concerns about the radar speed traps that actually do use the doppler effect; where the device is pointed at the front of the car. These are the hand held devices. The problem is the point of reflection on the car. If the device is not held steadily then the reflection point will move. If it started on the windscreen and then dropped to the front bumper, it would assume the speed of the car towards the operator to have been greater than it actually was.